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November 30, 2004

Study Reveals How Brain Adapts After Stroke

by Sam Savage

'Cyberglove' experiments could improve rehabilitation

HealthDayNews -- By challenging healthy people to learn unfamiliar, hand-dependent tasks, scientists are gleaning important insights into how patients overcome debilitating brain injury following a stroke.

The research may also yield better therapies for stroke victims, the scientists say.

As the researchers watched on real-time imaging machines, the brains of study participants lit up in key areas as they learned to manipulate a computer cursor while wearing a hi-tech "cyberglove."

"We're looking to see which areas of the brain are involved in this process, and what happens in areas of the brain as this learning process goes along," explained lead researcher Kristine Mosier, a professor of radiology and neuroscience at Indiana University School of Medicine.

According to Mosier, her team's research could improve post-stroke rehabilitation by "giving us a better idea of whether a particular type of therapy is going to be effective, or whether some other type of therapy might work even better."

The findings were presented Nov. 29 at the Radiological Society of North America annual meeting in Chicago.

Stroke, which occurs when blood flow stops to the brain, remains one of the leading causes of death and disability in the United States. Each year, stroke leaves thousands of Americans unable to move, speak or swallow due to damage in specific brain areas. Four million Americans are living with the effects of stroke, and the length of time to recover depends on its severity. Fifty percent to 70 percent of stroke survivors regain functional independence, but 15 percent to 30 percent are permanently disabled, according to the National Institute of Neurological Disorders and Stroke.

But the brain retains an amazing facility to adapt and change in the event of a stroke.

"One of the areas that's been a center of research over the past few decades is to see whether or not parts of the brain can 'pick up' the function that was previously carried out by the now-dead neurons in the stroke-affected area," Mosier said.

In experiments with 17 healthy adults, Mosier's team tried to simulate the challenges of what's called brain "mapping" -- the process by which the brain adapts to new, unfamiliar tasks. Brains "map" out new tasks from birth as we learn to grasp, walk or speak -- matching up sensory input from the environment with coordinated muscle movements.

Mosier said stroke victims have to go through what's called "remapping" if they hope to regain lost function, since brain areas that coordinated those tasks in the past may be useless now.

In their lab, Mosier's team hooked up the 17 participants to functional magnetic resonance imagery (fMRI) -- MRI scanning that shows real-time brain activity. The participants were then fitted with special computer-linked "cybergloves" that registered joint movements at 19 different points.

Specific combinations of finger movements allowed the participants to move a cursor on the computer screen. Normally, computer users rely on a mouse or touch pad to move a cursor, but in this case the participants had no such luxury.

"In that sense their brain is learning to remap," Mosier said. "It sounds very simple, but it's actually very difficult because their hand is not physically connected to the cursor on the computer screen."

All the participants eventually mastered this new, finger movement-dependent method of moving the cursor. And as they did so, specific neurological areas "lit up" as their brains came up with new ways to perform an otherwise familiar task.

"Areas that control hand movement are involved, of course, and you also see areas more toward the anterior part of the brain that we know are involved in learning," Mosier said.

The research is providing important clues to what might happen in similar circumstances in stroke-affected brains. "It helps answer questions like, 'Which areas of the brain are involved in which activities, and do they change over time?' This gives us a good way to predict, say, if you have a stroke affecting such-and-such area of the brain, how might other areas of the brain compensate for that."

The goal, Mosier said, is better post-stroke therapies tailored to specific patterns of stroke injury. "What our research is telling us is how much remapping may occur, giving us some idea of how that happens after stroke," she explained. "And what that will enable us to do is to build better rehabilitative strategies."